Most apartment homes in Annandale were built between 1960 and 1979. If a bid for your building says EPDM, the first job is not choosing a rubber sheet. It is finding out what already sits under it.
Building age by building size
The Census Bureau's 2020 to 2024 estimates count occupied homes in buildings of five or more units by the period the building went up. It counts homes, not roofs, so treat it as a map of building age only.
| Building put up | Homes in 5+ unit buildings | Share |
|---|---|---|
| 2000 to 2019 | 184 | 4.4 percent |
| 1980 to 1999 | 523 | 12.6 percent |
| 1960 to 1979 | 2,908 | 70.2 percent |
| 1940 to 1959 | 515 | 12.4 percent |
| 1939 or earlier | 12 | 0.3 percent |
The total is 4,142 homes. Of the 184 in newer buildings, every one is rented, and the estimates show no owner-occupied home in a building of that size from 2000 or later. The 1960 to 1979 group holds 722 owner homes and 2,186 rented ones, so most of these roofs answer to a landlord or a condominium board.
What that age means
The 2021 International Building Code bars a new roof covering over an old one where the old one is water soaked or deteriorated, or already carries two or more applications. An old building may have used up that allowance.
The single-ply trade association SPRI advises core cuts before re-covering over insulation, to learn whether a vapor barrier is trapping moisture. Over a metal deck damp insulation can dry downward, and over concrete it has no such route.
EPDM is one of the sheet types in that code's single-ply table, under the ASTM D4637 standard. The sheet's name tells you the polymer, not the roof underneath, so ask for the written plan for the old layers first and the membrane second.
An apartment building from the 1960s has a flat roof, so EPDM is the natural fit.
The Census counts homes, not roofs. Garden-style buildings can be pitched, a sheet like EPDM belongs on low-slope sections, and our reading is that pitched sections are a shingle or metal question.
Where the water goes
On an older flat section the useful picture is the exit for water. Photograph each drain, scupper and low corner after a rain, and note any standing water still there a day later. The drawing shows a drain at the low point and a low spot where water stays; it is a schematic with the slope exaggerated.
The same trade association advises inspecting low-slope roofs at least twice a year and after any major storm, and keeping the drains open.
Who decides
With 3,154 rented homes in these larger buildings, the person who signs is often a manager. Ask who holds the roof budget and the scope sign-off.
The county's permit page lists commercial replacement of less than 100 square feet of roof covering as not needing a permit and puts roof repairs on the permit side. It never names a membrane and does not say which list an apartment building uses, so describe your scope to the office on 703-222-0801.
It should say what comes off, what stays, how the seams are made and checked, and the ASTM number of the sheet. Lap seams are a long-standing subject in trade studies of EPDM, so ask about them in particular.
Questions
Nothing we opened says so. The county's permit page does not name EPDM or any other membrane.
The Census cannot tell you. It counts homes by the period the building was built, so check the records your association or landlord holds.
No. Single-ply sheets come in black, white and many colors, and color does not identify the material. The data sheet does.
The code allows a protective coating over existing single-ply without tear-off, but not where the roof is soaked or deteriorated. Ask for core cuts first.
A board treasurer or property manager. It shows how many homes share the roof decision, not what the roof is made of.
Photos of each drain, the low corners and any rooftop equipment, plus the building's rough age and unit count.
Nearby pages: the Annandale hub, EPDM roofs in Fairfax and EPDM roofs in Springfield. General reading: the TPO and EPDM guide for Northern Virginia, the flat roof guide and the materials page.
Checked 2026-10-14: Census Reporter, ACS 2020 to 2024 estimates, table B25127 (margins of error not shown); Fairfax County, when a permit is required. Code and trade-association text opened 2026-10-11: 2021 International Building Code chapter 15; SPRI single-ply FAQ.
Talk through the next step
Tell us the street, how many units, roughly when it was built and where the water leaves the roof. That settles whether EPDM is even on the table.
9220 Topaz St, Fairfax, VA 22031
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